`stylish-haskell` rejects source with indented module scope

The program below is rejected by `stylish-haskell`

``` haskell
module Blah where

import Prelude (IO,return)

main :: IO ()
main = do
return ()
```

with the parse error

```
Language.Haskell.Stylish.Parse.parseModule: could not parse Blah.hs: ParseFailed (SrcLoc {srcFilename = ".hs", srcLine = 5, srcColumn = 3}) "Parse error: main"
```

whereas `ghc` happily accepts that program.